[upstream] added per tier pool class rolling average latency

[guptask]

This change is 

[igchor]

Reviewable status: 0 of 7 files reviewed, 3 unresolved discussions (waiting on @guptask)

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cachelib/allocator/Cache.h line 89 at r1 (raw file):

  // TODO: come up with some reasonable number
  static constexpr unsigned kMaxTiers = 2;

Can we not include any references to tiers in this PR? We could add support for tracking latency per class, per pool, right?

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cachelib/allocator/CacheAllocator-inl.h line 2231 at r1 (raw file):

template <typename CacheTrait>
double CacheAllocator<CacheTrait>::slabsApproxFreePercentage(TierId tid) const {

I think this should not part of the latency tracking patch.

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cachelib/allocator/CacheAllocator-inl.h line 2236 at r1 (raw file):

template <typename CacheTrait>
AllocationClassBaseStat CacheAllocator<CacheTrait>::getAllocationClassStats(

Same here, you should probably just store allocLatenencyNs.

You can rebase onto #42 perhaps and just use getACStats which I've added if you think it will be easier.

[guptask]

cachelib/allocator/CacheAllocator-inl.h line 2231 at r1 (raw file):

Previously, igchor (Igor Chorążewicz) wrote…

I think this should not part of the latency tracking patch.

Done.

[guptask]

cachelib/allocator/CacheAllocator-inl.h line 2236 at r1 (raw file):

Previously, igchor (Igor Chorążewicz) wrote…

Same here, you should probably just store allocLatenencyNs.

You can rebase onto #42 perhaps and just use getACStats which I've added if you think it will be easier.

Done.

[guptask]

cachelib/allocator/Cache.h line 89 at r1 (raw file):

Previously, igchor (Igor Chorążewicz) wrote…

Can we not include any references to tiers in this PR? We could add support for tracking latency per class, per pool, right?

Done.

[guptask]

I'm closing this PR and raising a new one (#47) that is rebased against Igor's AC Stats upstream PR (#42)